The big cats pace rhythmically, their amber eyes riveted to the target. Tails swish, low growls rumble from their throats. Back and forth, back and forth.

Kimani, a 5-year-old African lion, attacks first. The 350-pound cat reared up on her hind legs and ripped away with her front paws. Today's prey: a giant roll of paper towels.

Quickly, she hunkered to the ground when Tunya, her 450-pound father, lunged into the cage. With one mighty swipe, he tried to knock the roll from its rope. No luck. Temporarily spent, Tunya turned for a drink of water, then sauntered back to the adjacent cage and sank down for a nap.

It's been like this for almost two months, ever since Christmas Day, when a Siberian tiger escaped its grotto and fatally mauled a 17-year-old San Jose man and injured two others. For 54 days, while their outdoor enclosure is being renovated, the big cats at the San Francisco Zoo have been stuck indoors - and out of public view - like giant, precocious children kept inside on a rainy day.

Animal keepers responsible for the big cats have had their own challenges - keeping the zoo's four lions and four tigers entertained and challenged, mentally and physically. Every day, they come up with a new game, a new routine, a new toy that might amuse the cats one day, bore them the next.

On Friday, the zoo keepers gave a Mercury News' reporter a behind-the-scenes look.

They've improvised toys for chewing, such as large plastic garbage cans and beef bones hidden in paper bags. They've shown the cats wildlife movies and documentaries, and all four lions and tigers seemed to enjoy them at first.

But Leanne, a 4-year-old Sumatran tiger, emerged as the only real movie fan. Disney's "Lion King" is her favorite, but she also didn't turn away for a second when she watched a documentary about elephant seals. The TV is kept just across from her cage.

All kinds of spices and smells - from human perfumes to urine from other animals - are sprinkled in straw or dripped on the cats' favorite chew toys.

"Rhino bedding has been a big hit," said Barbara Palmer, primary keeper of the big cats. That's straw the rhino marked or urinated on, straw the big cats love to smell and roll in. "They can tell a lot of things from urine that we can't come close to telling."

It's easier to keep the lions happy indoors. But the zoo keepers have worked extra hard to keep the cats entertained, because they have more stimulation when they are allowed to come-and-go outside.

"I was worried the cats would be very anxious, but we're not seeing that," said Jacqueline Jencke, chief of veterinary services for the zoo.

Zoo officials are waiting for the day the big cats can return to their outdoor play areas with rocks to climbs and people to watch.

Workers are finishing up renovations on the outdoor grottoes, but zoo officials still couldn't say late last week when they would re-open. A higher wall, new glass barriers and electrified wires are being added, steps some critics say might have prevented Tatiana the tiger from escaping the grotto. The grotto's wall for years was 4 feet lower than national guidelines, but will now be the recommended 16.4 feet.

San Francisco police suspended their investigation late last month into whether the three San Jose men - Carlos Sousa Jr., who was killed, and brothers Paul and Kulbir Dhaliwal - taunted Tatiana before she escaped. Police shot and killed the tiger after the attacks.

Tony, Tatiana's 16-year-old companion, is alone now, the only Siberian tiger left at the zoo. Keepers affectionately call him "our scaredy cat." He won't step on the scales or lie on a bench, as the other cats have been trained to do. During Friday's tour, he was noticeably quiet and resisted playing with his new plastic garbage can. It isn't clear, though, if he misses Tatiana. Tigers are less social than lions, the keepers say, but Tony interacts through a wire mesh door with the Sumatran pair, Leanne and George.

As Palmer, 41, bustled around, the big cats had on their "kitchen faces." They always hope she'll walk back to them with a treat, she said.

The keepers also have been teaching the animals to voluntarily lie down on a wooden bench, where they get treats for putting their noses on a target. It's training that allows them to be vaccinated or have blood samples taken without first being shot with a dart gun.

Leanne readily assumed the pose on Friday afternoon, the treat disappeared in a flash. She circled the bench again and lay down, hoping for one more treat.

Seven of the cats are housed in a long, large room that's usually open during public feedings, but those have been postponed during the renovations. Padang, a Sumatran tiger born in 1989, the oldest of the zoo's big cats, is kept in a separate exhibit.

"People come into this space with all kinds of expectations," Palmer said. To the cats, "it's just another room in the house, both a dining room and an entertainment center."

On Friday, the cats peered out of their cages, calmly studying the two new faces - a reporter and photographer - accompanying their keeper and doctor.

George shattered the silence with a quick lunge to the bars and a deep roar. Just as fast he chuffed, the soft sound big cats make when they're content.

"He's a young adult male and he's still trying to figure out how to assert himself," Palmer said.

For all the huff, George is the bathing king. He loves to soak in the bathtub, resting his big head on the edge of the tub.

For much of the day, the big cats sleep, moving around when darkness falls. And for some reason, every day at about 4:50 p.m., all of the lions roar.

Some day soon, the doors to the grottoes will slide open. But the keepers don't expect the cats to go charging outside.

They're getting so much attention inside, Palmer said. "I can bet money, which ones will come right back in."